Corrosion-proofing composition



United States Patent f 3,281,284 CORROSION-PROOFWG COMPOSITION Charles E. Dwors, Wickliffe, Ohio, assignor to The Lubrizol Corporation, Wicklitfe, Ohio, a corporation of Ohio No Drawing. Filed Mar. 25, 1963, Ser. No. 267,787 Claims. (Cl. 1486.16)

The present invention relates, as indicated, to a corrosion-proofing composition, which composition is adapted to form a protective coating on metal articles. In a more particular sense, it relates to a method for protecting metal articles, especially ferrous metal articles, against corrosion.

The corrosion of metal articles is of obvious economic significance in many industrial applications and, as a consequence, the inhibition of such corrosion is a matter of prime consideration. It is particularly significant to users of steel and other ferrous alloys. The corrosion of such ferrous metal alloys is largely a matter of rust formation, which in turn involves the overall conversion of the free metal to its oxides.

The theory which best explains such oxidation of ferrous metal surfaces postulates the essential presence of both water and oxygen. Even minute traces of moisture are sufficient, according to this theory, to induce the dissolution -of iron therein and the formation of ferrous hydroxide until the water becomes saturated with ferrous ions. The presence of oxygen causes oxidation of the resulting ferrous hydroxide to ferric hydroxide, which then settles out of solution and is ultimately converted to ferric oxide or rust. The above sequence of reactions can be prevented, or at least in large measure inhibited, by relatively impermeable coatings which have the effect of excluding moisture and/ or oxygen from contact with the metal surface. Such coatings are often exposed to high humidity, corrosive atmospheres, etc., and to the extent that these coatings are penetrated or otherwise harmed by such influences they become less desirable for the desired purpose. It is also important that such coatings adhere tightly to the metal surface and resist flaking, blistering, and other forms of loss of adhesion. A satisfactory corrosion-proofing composition, then, must have the ability to resist weathering, high humidity, and corrosive atmospheres such as salt-laden mist or fogs, air contaminated with industrial wastes, etc., so that a uniform protective film is maintained upon all or most of the metal surface.

Various derivatives of acid esters of phosphoric or phosphorothioic acids have been investigated by workers engaged in the task of providing protective coatings for metals. In US. Patents 2,080,299, for example, Benning et a1. propose the treatment of ferrous metals with phosphate acid esters or their alkali metal or ammonimum salts to prevent rusting. Somewhat similarly, Butler and Le Suer (US. Patent 2,861,907 and 2,820,723) find that salt-esters of complex phosphorothioic acids are effective in preventing or retarding the corrosion of metals.

Although such known derivatives of phosphoric and phosphorothioic acids have provided means for com-bating the corrosion of metals, they have not been completely satisfactory because of certain inherent shortcomings. The simple salt-esters of phosphoric acid are readily washed or abraded from a metal surface and thus provide complete protection only in a favorable environment.

3,281,284 Patented Get. 25,- 1963 The salt-esters of phosphorothioic acids, on the other hand, have the disadvantage, under certain conditions, of developing an objectionable odor reminisicent of hydrogen sulfide, particularly when a =film of such a salt-ester comes in contact with water or humid atmospheres.

A further disadvantage of these known derivatives of phosporic and phosphorothioic acids is that they form oily or tacky coatings which are not susceptible to the subsequent application of top-coats of siccative organic coating compositions such as paint, varnish, lacquer, enamel, primers, synthetic resins, and the like. Thus, their use has been limited to metal articles such as bulk castings, metal fasteners, firearm parts, iron cables, etc., which do not require .a dry-film protective coating.

It is, therefore, a principal object of the present invention to provide a novel, liquid corrosion-proofing composition.

Another object is to provide a method for inhibiting the corrosion of metal articles, especially ferrous metals and galvanized or phosphated ferrous metal articles.

A further object is to improve the adhesion of known, siccative organic coating compositions to metal articles.

A still further object is to improve the corrosion-proofing characteristics of known, siccative organic coating compositions.

These and other objects of the invention are realized by the provision of a liquid corrosion-proofiing composition adapted to form a protective coating on metal articles which comprises the combination of:

(A) the product obtained by mixing one mole of at least one aliphatic amine containing at least about 6 carbon atoms with from about 0.25 to about 2 moles of aqueous chromic acid and heating the mixture to remove substantially all water present, and

(B) an organic phosphate complex prepared by the process which comprises mixing one mole of phosphorus pentoxide, from about 0.2 to about 12.5 moles of a copolymer of .allyl alcohol and a styrene, and from about 0.3 to about 5.0 moles of an alkylphenol, and heating said mixture at a temperature within the range from about C. to about C.

In most instances, the corrosion-proofiing composition of this invention will comprise from about 0.05 to about 20 parts by weight of A per part of B.

Th-in films of the corrosion-proofiing composition per se of the present invention are remarkably effective in protecting metal articles, especially ferrous metal articles, against the ravages of corrosion. For some applications, pigments such as carbon black, powdered aluminum, iron oxide, red lead, zinc chromate, chrome green, etc., and pigment extenders such as finely divided silica, calcium carbonate, fullers earth, and the like may be added to the compositions of this invention for their known effects. If desired, a top-coat of a known siccative organic coating composition may be subsequently applied to a film of a composition of this invention so as to provide additional protection, decorative effects, etc.

The corrosion-proofing compositions of this invention are also useful as ingredients in known, siccative organic coating compositions such as solvent-based paints, varnishes, lacquers, primers, synthetic resins, and enamels, to which compositions they imp-art enhanced corrosion-inhibitiug characteristics. The siccative organic coating composition may also be an aqueous base or emulsion paint such as synthetic latex paints derived from acrylic resins, polyvinyl alcohol resins, alkyd resins, etc., by emulsification thereof with water, as well as water-soluble paints derived from water-soluble alkyd resins, acrylic resins, and the like. Such siccative organic coating compositions may contain conventional improving agents such as pigment extenders, anti-skinning agents, driers, gloss agents, color stabilizers, etc. When used for this purpose, i.e., to improve known coating compositions, a minor proportion, generally from about 0.1 to about 25% of the corrosionproofing composition of this invention is blended with a major proportion, generally from. about 99.9 to about 75%, of a siocative organic coating compositions, all parts being by Weight.

COMPONENT A This component, as indicated, is prepared by mixing one mole of at least one aliphatic amine containing at least about 6 carbon atoms with from about 0.25 to about 2 moles of aqueous chromic acid and heating the mixture to remove substantially all water present. The product of this reaction is believed to be principally an amine salt of chromic acid, although other materials such as amine dichroma-te, amine oxidation products (chromic acid is known to be a strong oxidizing agent), etc., may be formed and contribute substantially to its properties. In most instances, it is preferred to use amounts of the amine and the aqueous chromic acid within the range from the stoichiometric amounts for the amine acid chromate (equimolar proportions of the amine and aqueous chromic acid) to the stoichiometric amounts for the normal amine chromate (one mole of the amine and 0,5 mole of aqueous chromic acid). It is also desirable in some instances to use 2 or more products derived from reactions involving ditterent amounts of the amine and the aqueous chromic acid. Of course, proportions of the amine and aqueous chromic acid outside of the scope of the broad range of one mole of the amine and from about 0.25 to about 2 moles of aqueous chromic acid may be employed, if desired, although the products of such reaction will contain excess amine or excess chromic acid and are, therefore, uneconomical and not preferred for the purposes of this invention.

Amines useful for the preparation of component A includes any of the various aliphatic primary, secondary, and tertiary monoamines and polyamines containing a total of from about 6 to about 30 or more carbon atoms, which amines may also contain substituents such as chloro, fluoro, bromo, nitro, nitroso, ether, ester, sulfide, etc. Examples of such amines include trie-thyl amine, di-n-butylamine, di-isobutylamine, tri-isobutylamine, 6-chloro-n-hexylamine, 3-amino-n-heptane, 2-ethylhexyl amine, tertiaryoctyl primary amine, 3,5,5-trirnethyl-hexylamine, n-decylamine, di-n-decylamine, tri-n-decylamine, tertiary-dodecyl primary amine, tertiary-octadecyl primary amine, cety1- amine, n-octadecyl amine, oleylamine, eicosylamine, docosylamine, hexacosylamine, tri-acontylamine, hexatriacontylarnine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexarnine, cyclohexylamine, dicyclohexylamine, isooctenyl amine, '2-butoxy ethylamine, aminoethyl oleate, aminopropyl stearate, bis-(dimethylaminopropyl) amine, n-a-minopropyl-octadecyl amine, aminornenthane, etc. From the foregoing, it will be noted that the aliphatic radical may possess an open chain or cyclic structure.

A particular preference is expressed for monalkyl primary amines conforming to the structure RNH where R is an alkyl radical. Examples of such monalkyl primary amines include n-hexylamine, Z-ethylhexylamine, laurylamine, cetylamine, and tertiary-ealkyl primary amines. The tertiary-alkyl primary amines referred. to conform to the characterizing structure wherein a tertiary carbon atom, i.e., one devoid of hydrogen atoms, is bonded to a primary amino radical, i.e., NH Such tertiaryaalkyl primary amines should contain at least about 6 and generally not more than about 30 carbon atoms in the tertiary alkyl substituents. In most instances, the tertiary-alkyl substituent will con-tain from about 10 to about 24 carbon atoms. Specific examples of tertiarysalkyl primary amines useful for the purposes of this invention include tertiary-octyl primary amine, tertiary-decyl primary amine, tertiary-dodecyl primary amine, tertiary-tetradecyl primary amine, tertiary-hexadecyl primary amine, tertiary-heptadecyl primary amine, tertiary-octadecyl primary amine, tertiary-eicosyl primary amine, tertiary-docosyl primary amine, tertiary-tetracosyl primary amine, tertiary-triacontyl primary amine, etc. It is not necessary to use a single tertiary-alkyl primary amine. In fact, it is generally more convenient to use a commercial mixture of such amines wherein the tertiaryalkyl substituent present contains from about 10 to about 24 carbon atoms. A typical mixture of such commercial tertiary-alkyl primary amines, for example, consists of tertiary-ralkyl primary amines containing from about 12 to about 15 carbon atoms, said mixture averaging about 12 carbon atoms per amine molecule. This mixture, available under the trade designation Pri-mene 81R, contains about 85% of tertiary-do-decyl primary amine, about 10% of tertiary-pentadecyi amine, and less than about 5% of amines having less than l2.or more than 15 carbon atoms. Another mixture of commercial tertiary-alkyl primary amines suitable for the purposes of the present invention consists of tertiary-alkyl primary amines having from about 18 to about 24 carbon atoms and averaging about 20 carbon atoms per amine molecule. This mixture of tertiary-alkyl primary amines contains about 40% of tertiary ootadecyl primary amine, about 30% of tertiary-eicosyl primary amine, about 15% of tertiary-docosyl primary amine, about 10% of tertiary-tetracosyl amine, and about 5% of amines outside the C to C range.

Tertiary-alkyl primary amine mixtures such as described above can be prepared by methods within the knowledge of those skilled in the art. For example, such mixtures may be prepared from polypropylene or polybutene fractions or mixtures thereof. Thus, a selected polymer fraction composed of mixed polyolefins within the desired molecular Weight range can be converted tothe corresponding tertiaryaalkyl primary amines as follows. The selected polyolefin fraction is first hydrated by means of sulfuric acid and water to convert it to the corresponding alcohols. The alcohol mixture is then converted to alkyl chloride by the reaction with dry hydrogen chloride. Finally, the alkyl chloride mixture is condensed under pressure with ammonia to produce the desired tertiaryalkyl primary amine mixture. Specific methods of preparing terti-ary-alkyl primary amines are described in the Journal of Organic Chemistry, Volume 20 (1955), beginning at page 295.

The aqueous chromic acid employed in the preparation of component A will range from a saturated aqueous solution of chromic acid (contains about 74% of H CrO to a dilute aqueous solution containing as little as 5 or 10% of H CrO For the most convenient and economical operation, it is generally preferred to use saturated or near-saturated aqueous solutions of chromic acid.

The conditions of time and temperature employed for the reaction of the amine and the aqueous chromic acid are not critical. It is only necessary that the two reactants be reacted under conditions such that substantially all of the Water present will be removed. Thus, for example, the reactants may be maintained at the boiling point until the Water ceases to distill from the reaction mass. A more rapid and economical removal of Water may be eifected by heating the reaction mass at a temperature of, say, 60100.C. under reduced pressure until no more water distills. In any event, the process is carried out until water no longer distills from the reaction vessel. If desired, the somewhat viscous product may be diluted with a solvent such as benezne, toluene, xylene, aromatic petroleum spirits, naphtha, etc., to facilitate handling.

The following examples are submitted to illustrate specific modes of preparing component A. They are presented for purposes of illustration only and are not to be construed as limiting the scope of the present invention, except as the latter is defined by the appended claims.

Example 1 122 parts of water and 162 parts of CrO are mixed at 2540 C. to yield a concentrated aqueous solution of chromic acid. 620 parts of a commercial mixture of C C tertiary-alkyl primary amines (2 moles of amine per mole of aqueous chromic acid) is added to the aqueous chromic acid solution over a period of 0.5 hour. An exothermic reaction carries the temperature from 25 C. to about 80 C. The Whole is then stirred for about 2 hours at 80100 C. and then the pressure is reduced to about 50 mm. Hg to remove substantially all of the water present. 47 parts of organic distillate is separated from the aqueous distillate and is recharged to the reaction vessel. To facilitate handling the somewhat viscous product 90 parts of aromatic petroleum spirits is added. The product, a 90% solution of the active chemical in aromatic petroleum spirits, shows the following analyses.

Percent chromium 9.5 Percent nitrogen 5.1

Example 2 180 parts of water and 238 parts of CrO are mixed at 2540 C. to yield a concentrated aqueous solution of chromic acid. 620 parts of a commercial mixture of C C tertiary-alkyl primary amines (1.36 moles of amine per mole of aqueous chromic acid) is added to the aqueous chromic acid over a period of about 0.5 hour. Thereafter, the whole is processed in the same manner set forth in Example 1 above. The product, a 90% solution of the active chemical in aromatic petroleum spirits, shows the following analyses.

Percent chromium 12.6 Percent nitrogen 4.5

Example 3 200 grams of CrO is mixed with 200 grams of water to form a concentrated aqueous solution of chromic acid. Such solution is then added to 764 grams of a commercial mixture of C C tertiary-alkyl primary amines (2 moles of amine per mole of aqueous chromic acid) over a period of 0.7 hour. An exothermic reaction causes the temperature to rise to about 37 C. One liter of benzene solvent is added to the reaction vessel and the contents are refluxed, using a side-arm water trap to remove Water. After substantially all of the Water is removed, the benzene solvent is removed at 87 C./ 50 mm. Hg. The product, a brown viscous liquid, shows the following analyses.

Percent chromium 11.0 Percent nitrogen 5.7

Example 4 In the same manner set forth in Example 3, 800 grams of concentrated aqueous chromic acid (from 400 grams of CrO and 400 grams of water) and 764 grams of a commercial mixture of C12 C15 tertiary-alkyl primary amines (equirnolar proportions of the amine and the aqueous chromic acid) are processed to yield a product useful for the purposes of this invention. The product, a dark brown viscous liquid, shows the following analyses.

Percent chromium 17.1 Percent nitrogen 4.46

6 Example 5 In the same manner set forth in Example 3, 200 grams of concentrated aqueous chromic acid (from grams each of CrO and water) and 573 grams of a commercial mixture of 0 -0 tertiary-alkyl primary amines (3 moles of the amine per mole of aqueous chromic acid) are processed to yield a product useful for the purposes of this invention. The product, a clear brown viscous liquid, shows the following analyses.

Percent chromium 7.40 Percent nitrogen 6.11

Example 6 A product is prepared in the same manner set forth in Example 3 except that 596 grams of a commercial mixture of C C tertiary-alkyl primary amines averaging about 20 carbon atoms per molecule is employed as the amine reactant.

Example 7 387 grams of CrO is mixed With 244 grams of Water to form a concentrated aqueous solution of chromic acid solution. Such solution is added to 1000 grams of 2 ethylhexylamine (2 moles of amine per mole of aqueous chromic acid) over a period of 1.75 hours at 25 96 C., the temperature rising as indicated due to the exothermic nature of the reaction. After all of the aqueous chromic acid has been added, the Whole is stripped under a nitrogen atmosphere at 76 C./ mm. Hg to remove substantially all of the water present. The product, a brown liquid, shows the following analyses.

Percent chromium 14.56 Percent nitrogen 6.23

COMPONENT B This component, an organic phosphate complex, is described in US. patent application, Serial No. 50,844, filed August 22, 1960, now U.S. Patent 3,055,865. It is prepared, as indicated earlier, by mixing one mole of phosphorous pentoxide, from about 0.2 to about 12.5 moles of a copolymer of allyl alcohol and a styrene, and from about 0.3 to about 5.0 moles of an alkylphenol and heating such mixture at a temperature within the range from about 75 C. to about C. In the interest of not unduly lengthening the present specification, it is intended that the disclosure of the above identified patent be considered as forming a part of the present specification.

The copolymer referred to is a copolymer of 10 to 90 mole percent of allyl alcohol With 90 to 10 mole-percent of a styrene. Especially useful for the purposes of this invention are copolymers prepared from approximately equimolar amounts of the two monomers and having an average molecular Weight Within the range from about 500 to about 5000. A particular preference is expressed for a copolymer of approximately equimolar amounts of allyl alcohol and styrene having an average molecular weight of about 1l001150. Such a copolymer is available under the trade designation Polyol X-450. Similar ecopolymers of lesser or greater average molecular weight are also available, such as Monsanto RJ-100, which has an average molecular weight of about 1580.

The term a styrene as used herein refers to styrene or any of the various substituted styrenes such as halogensubstituted styrenes, hydrocarbon-substituted styrenes, alkoxy-styrenes, acyloxy-styrenes, nitro-styrenes, etc. Ex-

amples of such substituted styrenes include para-chloro- The alkylphenol may be either a mono-.alkyl or polyalkyl monohydric or polyhydric phenol. The alkyl groups may be of any size, ranging from methyl up to alkyl groups derived from olefin polymers having molecular weights as high as 50,000 or more, and may contain olefinic linkages. The alkyl group may also have a cyclic structure, if desired. Preferably the alkylphenol is. a mono-alkyl phenol in which the alkyl group is acylic and contains from 1 to about 30 carbon atoms, perferably at least about 4 carbon atoms. Typical examples of useful alkylphenols include, e.g., ortho, meta, and paracresols; ortho, meta, and para-ethylphenols; para-isopropylphenol, paraaallylphenol, para-tertiary butylphenol, ortho-n-amylphenol, para-tertiary amylphenol, n-hexylphenol, cyclohexylphenol, methylcyclohexylphenol, heptylphenol, diisobutylphenol (i.e., i'sooctylphenol), n-decylphenol, cetylphenol, oleylphenol, n-octadecylphenol, waxalkylated alpha-naphthol, wax-alkylated phenol, and polyisobutene-substituted phenol in which the polyisobutene substituent contains from about 12 to about 96 carbon atoms. The alkylphenol may also contain substituent groups such as, e.g., ohloro, fluoro, nitro, alkoxy, sulfide, nitroso, etc. A particular preference is expressed for para-tertiary amylphenol. Also useful are alkylated polyhydric phenols such as alkylated resorcinols, alkylated catechols, alkylated pyrogallols, and their substitution products. Thus n-octylresorcinol, laurylcatechol, or cetylpyrogallol may be used as the alkylphenol.

The exact manner in which the phosphorus pentoxide, oopolymer, and alkylphenol are mixed and heated to form component B is not particularly critical. Ordinarily, all three reactants are mixed and then simply heated. In some instances, however, it is desirable to carry out the process in stepwise fashion. For example, one may first mix the phosphorus pentoxide with either the copolymer or the alkylphenol, heat the mass at about 75150 0., add the remaining reactant, and then continue heating. Ordinarily the reaction is carried out in the presence of a solvent and the solvent then removed, if desired, by distillation when the reaction is completed. Suitable solvents for the reaction include, e.g., xylene, benzene, cyclohexene, chlorobenzene, trichloroethylene, tetrachloroethylene, aromatic petroleum spirits, ethylene dichloride, and dioxane. Other inert, relatively volatile solvents may also be used. The reaction may also be carried out in the absence of a solvent and a solvent added later, if desired, to the resulting solvent-free organic phosphate complex. The reaction appears to involve first a reaction between phosphorus pentoxide and the copolymer, followed by a reaction of this intermediate product with the alkylphenol. Presumably this latter reaction is a transesterification. The reaction mixture is at first cloudy and viscous, but as it proceeds the cloudiness and high viscosity disappear and the final product mixture is a relatively clear solution. The optimum reaction time is about 4 to 6 hours, although a suitable product can be obtained at any point within a period from about 0.5 to about 10 hours or more.

The precise chemical composition of the organic phosphate #complex employed as component B herein is not known. It is believed, however, that the phosphorus pentoxide phosphorylates the organic hydroxy compounds present to form complex phosphate esters. Other reactions such as polymerization and/ or 'etherification may also occur during the process and thus this component is best described in tenms of the manner of its preparation.

The following examples are presented to illustrate specific modes of preparing component B. All parts are by weight unless otherwise specified. The acid number referred to is carried out in accordance with ASTM procedure D 974- 5 T using the specified end-point indicator.

Example 8 A mixture of 1412 parts (11.2 moles) of a 1:1 molar copolymer of allyl alcohol and styrene having an average molecular weight of about 1100-1150, 168 parts. (1.0 mole) of para-tertiary amylphenol, 68 parts (0.5 mole) of phosphorus pentoxide, and 1648 parts of xylene solvent is prepared at room temperature and then heated at the reflux temperature, ca. 141 C., for 6 hours. The reaction mixture is stirred throughout this period and the water of reaction is removed by means of a side-arm water trap. At the end of this time the xylene is removed by distillation to yield a plastic, non-viscous mass. This residue, while still hot, i.e., at about C., is diluted with 824 parts of isobutyl alcohol. The product, a 65% solution of the organic phosphate complex in isobutyl alcohol, shows the following analyses.

Percent phosphorus 1.16 Acid number 1 22.6

1 Phenolphthalein indicator.

Example 9 A mixture of 313 parts (0.284 mole) of the copolymer described in Example 8, 314 parts (0.786 mole) of mono- (polyisobutene-substituted) phenol wherein the polyisobutene substituent contains an average of about 22 carbon atoms, 31 parts (0.218 mole) of phosphorus pentoxide, and 660 parts of xylene is heated to the reflux tem perature, ca. C., and maintained at this temperature for 6 hours while water is removed by means of a sidearm water trap. Substantially all of the xylene is removed by distillation of the mass at 140 C./ 20 mm. Hg and then the residue is diluted with 350 parts of isobutyl alcohol. The product, a 65% solution of the organic phosphate complex in isobutyl alcohol, shows the following analyses.

Percent phosphorus 1.35 Acid number 16.7

1 Bromphenol blue indicator.

Example 10 800 parts (0.73 mole) of the copolymer described in Example 8, 27 2 parts (1.66 moles) of para-(tertiary amylphenol, 80 parts (0.57 mole) of phosphorus pentoxide, and 1148 parts of xylene solvent are introduced into a reaction vessel fitted with a stirrer and a side-arm water trap. The whole is heated at the reflux temperature (132140 C.) for 6 hours while the water of reaction is removed by means of the sideaarm water trap. The pressure on the reaction vessel is then lowered to 30 mm. Hg to remove the xylene solvent. After all of the xylene solvent has been removed, 616 parts of isobutyl alcohol is added. The resulting product, a 65% solution of the desired organic phosphate complex in isobutyl alcohol, shows the following analysis.

Percent phosphorus2.0

Additional examples of organic phosphate complexes useful as component B are shown in Table I. They are prepared in the same manner set forth in Example 8 using the indicated quantities of reagents.

TABLE I Moles of the indicated starting materials to be employed Ex. No. Alkylphenol Co- Phosphorus polymer 1 Pentoxide Identity Moles 11 0. 87 Para-tertiary amyl- 16. 2 4

pben 0 8 do 12 4 1 8 d0 12 4 5 Heptylphen 12 4 5 Pararcresol 12 4 5 N onylphenol 12 4 1 As described in Example 8.

The corrosion-proofing compositions of this invention and known coating compositions containing the same may be applied to metal articles by any one of the methods ordinarily used in the paint and varnish industry such as brushing, spraying, dip-coating, flow-coating, roller-coating, and the like. Such compositions may be adjusted for the particular method of application selected by adding a suitable amount of a solvent such as benzene, xylene, mesitylene, aromatic petroleum spirits, turpentine, or other appropriate solvents. The metal surface which has been thus coated is then dried either by exposure to air or by means of a baking procedure. A dried film thickness of the corrosion-proofing composition of this invention or of a known coating composition containing the same ranging from about 0.01 mil to about 4 mils, preferably 0.02-2 mils, is usually required to provide adequate protection for the metal article. Coatings heavier than 4 mils can be used, of course, Where such heavier coatings provide additional wanted benefits. It is desirable in some instances to admix the corrosion-proofing composition of this invention with a pigment such as titanium dioxide, chrome green, aluminum powder, carbon black, iron oxide, organic pigments, or zinc chromate. For some applications, it is also desirable to include conventional improving agents such as pigment extenders, anti-skinning agents, driers, gloss agents, color stabilizers, etc.

As indicated earlier, the corrosion-proofing compositions of this invention comprise from about 0.05 to about 20 parts by weight of component A per part of component B. When components A and B are mixed there is a slight, but perceptible, rise in temperature. Analytical evidence indicates that upon mixing, at least a portion of the hexavalent chromium in component A is reduced to trivalent chromium. This phenomenon is believed to be at least partially responsible for the excellent corrosion-proofing characteristics of the compositions of this invention. In any event, components A and B may be pre-mixed and packaged, mixed just prior to use, or blended with a known siccative organic composition prior to packaging or prior to application to a metal article.

A number of laboratory tests were carried out to determine the utility of the herein described corrosionproofing compositions. Unless otherwise indicated, all parts and percentages are by weight. In the paint and varnish industry it is accepted practice to make additions and/or substitutions of ingredients in coating compositions on a non-volatile material basis so as to exclude consideration of any inert, volatile solvents such as alcohols, ketones, turpentine, naphtha, etc., present in the compositions. In the following examples, percent NVM or parts NVM of a specified material has this accepted meaning.

EXAMPLE A Six clean 4-inch by 8-inch panels of SAE 1020 20- gauge cold-rolled steel were spray-coated, respectively, with a known, water-soluble black bake paint and five experimental paints prepared by replacing a minor proportion of the resin in such known paint with compositions of this invention. After the panels had been coated, they were baked in an oven for 30 minutes at 375 F. The dried film thickness in each instance was determined to be 09:0.1 mil.

The coated and baked panels were then subjected to the Salt Fog Corrosion test described in ASTM procedure B117-57T. In this test a mist or fog of percent aqueous sodium chloride is maintained in contact with the panels for a predetermined time (in this case, 48 hours) at 95 '-2 F. After 48 hours exposure, the panels were removed from the test chamber, scraped vigorously with a putty knife and water-washed to remove any non-adherent coating, and then inspected to determine the percent of coating still adhered to the metal substrate. The test results are given in Table H.

TABLE II.SALT FOG CORROSION TEST, 48 HOURS Paint employed to form the Percent of coating coating on the test panel: still adhered Known water-soluble paint S 1 (control) 58 Paint S modified in that 1% NVM of the resin is replaced with 1% NVM of a mixture of 3 parts NVM of the product of Example 1 and 1 part NVM of the product of Example 10 Paint S modified in that 3% NVM of the resin is replaced with 3% NVM of a mixture of 3 parts NVM of the product of Example 1 and 1 part NVM of the product of Example 10 Paint S modified in that 7% NVM of the resin is replaced with 7% NVM of a mixture of 3 parts NVM of the product of Example 1 and 1 part NVM of the product of Example 10 Paint S modified in that 1% NVM of the resin is replaced with 1% NVM of a mixture of equal parts NVM of the products of Examples 1 and 10 70 Paint S modified in that 3% NVM of the resin is replaced with 3% NVM of a mixture of equal parts NVM of the products of Examples 1 and 10 90 Prepared by milling in a paint-shaking apparatus 150 parts of a phenolic resin (67% solution in water-butanol),

3 pants of carbon black, 10 parts of isobutanol, and 50 parts of water.

It will be noted that small proportions of the corrosionproofing compositions of this invention substantially improved the adhesion of a known water-soluble bake paint to plain steel.

EXAMPLE B A series of experiments like that described in Example A was carried out, except that in lieu of the plain steel panels, phosphated steel panels were used. The phosphated panels were prepared by first cleaning steel panels of the type described in Example A with an aqueous cleanser compounded from water and one ounce per gallon of an alkaline cleaning compound, water-rinsing the cleaned panels, spray-phosphating them for one minute at 160170 F. with an aqueous phosphating solution containing 0.15% of zinc ion, 0.10% of sodium ion, 0.74% of calcium ion, 2.0% of nitrate ion, and 0.56% of phosphate ion, and finally rinsing them at room temperature with an aqueous sealing solution containing 0.128% of calcium dichromate.

In the present instance, the panels which had been subjected to the Salt Fog Corrosion test were inspected to determine the percent of rust-free coating remaining thereon (see Table III).

TABLE IIISALT FOG CORROSION TEST, 750 HOURS Paint employed to form the coating Percent of rust-free on the phosphated steel test panel: coating Known Water-soluble paint S (control) 68 Paint S modified in that 1% NVM of the resin is replaced with 1% NVM of a mixture of 3 parts NVM of the product of Example 1 with 1 part NVM of the product of Example 10 Paint S modified in that 7% NVM of the resin is replaced with 7% NVM of a mixture of 3 parts NVM of the product of Example 1 with 1 part NVM of the product of Example 10 Paint S modified in that 1% NVM of the resin is replaced with 1% NVM of a mixture of equal parts NVM of the products of Examples 1 and Paint S modified in that 3% NVM of the resin is replaced with 3% NVM of a mixture of equal parts NVM of the products of Examples 1 and 10 Paint S modified in that 7% NVM of the resin is replaced with 7% NVM of a mixture of equal parts NVM of the products of Examples 1 and 10 1 1 It will be noted that the combination of a phosphated steel panel and a superimposed Water-soluble bake paint containing a corrosion-proofing composition of this invention is very eiiective in reducing rust-through over a long period of time in a highly corrosive atmosphere.

EXAMPLE C A number of steel panels of the type described in Example A were brush-coated, respectively, with three different organic solvent-based primers and such primers blended with small proportions of corrosion-proofing compositions of the present invention. The coated panels were allowed to air-dry for seven days (dried film thickness: 2.1:03 mil) and then they were subjected to Cross- Hatch Adhesion and Water Immersion tests.

The Cross-Hatch Adhesion test is carried out as follows: The panel under test is immersed for 16 hours in a water bath at 160 F. and then cross-hatched with a pointed steel instrument so as to yield eleven parallel oneinch long scribes spaced -inch apart and a like number of intersecting scribes at right angles thereto. Adhesive cellophane tape is applied to the scribed area and then the tape is removed. The scribed area is rated for coating adhesion on a scale of O to 10, 10 representing a perfect result (no loss of coating) and representing a panel which has lost all of the coating from the scribed area.

In the Water Immersion test, the test panel is completely immersed for 16 hours in a water bath maintained at 160 F. The panel is then removed and inspected for evidence of loss of adhesion (blistering, flaking, etc.).

The test results are shown in Table IV.

TABLE IV.CROSS-HAT%EHS IASND WATE R-IMME RSION Cross- Primer Employed to Coat Hatch Water Immersion Test,

the Steel Test Panel Adhesion Inspectors Remarks Value Orange Fast Drying Metal Moderately to densely cov- Primer T (control). vered with large (ca. }4- inch diameter) blisters. Primer T plus 1% NVM each No blisters or flaking.

of the products of Examples 2 and 8. Alkyd Ohromate Primer U 3 Densely covered with small (control). (ca. lz-inch diameter) blisters. Primer U plus 1% NVM each 10 No blisters or flaking.

of the products of Examples 2 and 8.

Gray Primer V (control) 1 Densely covered with moderate size (ca. Mrs-inch diameter) blisters.

Primer V plus 1% NVM each 10 No blisters or flaking.

of that sproducts of Examples 2 an Example C. The test results are given in Table V.

TABLE V.WATER-IMMERSION TEST Primer Employed to Coat the Galvanized Steel Test Panel Inspector's Remarks Orange Fast Drying Metal Primer T (control).

Primer T plus 1% NVM each of the products of Examples 2 and 8.

Algyg Chromate Primer U (con- Primer U plus 1% NVM each of the products of Examples 2 and 8.

Gray Primer V (control) Primer V plus 1% NVM each of the products of Examples 2 and 8.

Moderately covered with large blisters.

One small cluster of moderate size blisters.

Moderately to densely covered with small blisters.

No blisters or flaking.

Moderately to densely covered with small blisters. No blisters or flaking.

It will be noted that the corrosion-proofing compositions of this invention greatly improve the adhesion of known organic solvent-based primers to galvanized steel. The poor adhesion of conventional paints to galvanized ferrous metal articles constitutes a Widely recognized problem in the metal finishing industry. Thus, the present invention provides a convenient way to alleviate this problem.

EXAMPLE E Several panels were coated in a manner similar to that set forth in Example C except that pre-rusted steel panels were used in lieu of plain steel panels. The pre-rusted panels were prepared by exposing steel panels outdoors for two months. After the coated panels had dried, they were subjected to the Water Immersion test described in Example C. The test results are shown in Table VI.

TABLE IV .WATER-IMMERSION TEST Primer Employed to Coat the Inspectors Remarks Pre-Rusted Steel Test Panel Primer U plus 1% NVM each of the products of Examples 2 and 8. Gray Primer V (control) Primer V plus 1% NVM each of the Moderately to densely covered with large blisters. No blisters or flaking.

Moderately to densely covered with moderate size blisters. No blisters or flaking.

A few small blisters. No blisters or flaking.

products of Examples 2 and 8.

Thus, it Will be noted that the corrosion-proofing compositions of this invention are elfective in improving the adhesion of known, organic solvent-based primers to rusted metal articles.

In addition to their utility as protective coating materials and improving agents for'known coating materials intended for application to the surfaces of ferrous metal articles, galvanized ferrous metal articles, and phosphated metal articles, the corrosion-proofing compositions of this invention are also useful in protecting non-ferrous metals and alloys thereof such as aluminum, magnesium, cadmium, copper, brass, bronze, white metal, etc., against corrosion. They are also useful in protecting plated metal surfaces such as copper-plated, nickel-plated, and cadmium-plated ferrous metal articles against corrosion. They are also useful as protective coating materials and improving agents for known coating materials intended for application to chromated aluminum or chromated zinc metal articles, i.e., aluminum or zinc metal articles which have been treated with an aqueous solution of chromic acid or a derivative thereof such as a metal chromate or dichromate, ammonium chromate, etc.

Particularly fine results are obtained when the corrosion-proofing compositions of the present invention are applied to a metal article which has been phosphated by means of a novel aqueous phosphating solution containing as essential ingredients zinc ion, phosphate ion, nitrate ion, and a cation selected from the group consisting of lithium, beryllium, magnesium, calcium, strontium, cadmium, and barium. Example B herein sets forth the excellent results which are obtained when a metal article is phosphated with such novel phosphating solution and then coated with a corrosion-proofing composition of the present invention. Aqueous phosphating solutions which contain the aforementioned ions provide a dense, adherent, micro-crystalline or amorphous phophate coating upon a metal article and are described in detail in co-pending U.S. application, Serial No. 373,449, filed August 10*, 1953, now U.S. Patent No. 3,090,709. It is intended that the entire disclosure of Serial No. 373,449 be incorporated herein by reference.

What is claimed is:

1. A liquid corrosion-proofing composition adapted to form a protective coating on metal articles which comprises the combination of:

(A) the product obtained by mixing one mole of at least one aliphatic amine containing at least about 6 carbon atoms with from about 0.25 to about 2 moles of aqueous chromic acid and heating the mixture to remove substantially all water present, and

(B) an organic phosphate complex prepared by the process which comprises mixing one mole of phosphorus pentoxide, from about 0.2 to about 12.5 moles of a copolymer of allyl alcohol and a styrene, and from about 0.3 to about 5.0 moles of an alkylphenol, and heating said mixture at a temperature within the range from about 75 C. to about 150 C.

2. A corrosion-proofing composition in accordance With claim 1 characterized further in that (A) is present in an amount from about 0.05 to about 20 parts per part of (B).

3. A corrosion-proofing composition in accordance with claim 1 characterized further in that the aliphatic amine of (A) is a monoalkyl primary amine.

4. A corrosion-proofing composition in accordance with claim 1 characterized further in that the aliphatic amine of (A) is a mixture of C to C tertiary-alkyl primary amines.

5. A corrosion-proofing composition in accordance with claim 1 characterized further in that the copolymer of (B) is a copolymer of about equimolar amounts of allyl alcohol and styrene and has an average molecular weight in the range of 1,100 to 1,150. 1

6. A corrosion-proofing composition in accordance with claim 1 characterized further in that the alkylphenol of (B) is para-tertiary amplphenol.

7. A method for inhibiting the corrosion of a metal article which comprises applying thereto a film comprising the composition of claim 1.

8. A method in accordance with claim 7 wherein said film comprises a major proportion of a siccative organic coating composition and a minor proportion of the composition of claim 1.

9. A method in accordance with claim 8 wherein the metal article is a phosphated metal article.

10. A metal article which has been protected against corrosion in accordance with the method of claim 7. 

1. A LIQUID CORROSION-PROOFING COMPOSITION ADAPTED TO FORM A PROTECTIVE COATING ON METAL ARTICLES WHICH COMPRISES THE COMBINATION OF: (A) THE PRODUCT OBTAINED BY MIXING ONE MOLE OF AT LEAST ONE ALIPHATIC AMINE CONTAINING AT LEAST ABOUT 6 CARBON ATOMS WITH FROM ABOUT 0.25 TO ABOUT 2 MOLES OF AQUEOUS CHROMIC ACID AND HEATING THE MIXTURE TO REMOVE SUBSTANTIALLY ALL WATER PRESENT, AND (B) AN ORGANIC PHOSPHATE COMPLEX PREPARED BY THE PROCESS WHICH COMPRISES MIXING ONE MOLE OF PHOSPHORUS PENTOXIDE, FROM ABOUT 0.2 TO ABOUT 12.5 MOLES OF A COPOLYMER OF ALLYL ALCOHOL AND A STYRENE, AND FROM ABOUT 0.3 TO ABOUT 5.0 MOLES OF AN ALKYLPHENOL, AND HEATING SAID MIXTURE AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 75*C. TO ABOUT 150*C. 